發(fā)布時(shí)間：2018-08-28 14:42

【摘要】：在燃料的所有利用形式中,燃燒過程是將燃料化學(xué)能轉(zhuǎn)化為熱能的必經(jīng)過程。由于燃料構(gòu)成比較復(fù)雜,并且燃燒產(chǎn)物多涉及到幾種物質(zhì)的混合,這就決定了在分析燃燒效率時(shí)很難用熱力學(xué)第一定律加以衡量。燃料利用過程需要具體化分析,不能僅局限在過程始末的分析,更要對(duì)過程本身的變化加以衡量。本文分別以碳、甲烷、辛烷三種不同狀態(tài)的燃料為例,并以單耗分析理論為依據(jù)對(duì)此三種燃料所代表的各種狀態(tài)的燃料(?)進(jìn)行簡化分析,并以燃料高位發(fā)熱量來計(jì)算在不同溫度下這三種燃料燃燒過程的反應(yīng)焓、反應(yīng)自由焓、反應(yīng)熵及不可逆損失占發(fā)熱量的比重并畫出關(guān)系曲線圖。結(jié)果顯示,純碳燃燒的反應(yīng)熵為正值且不存在水蒸氣相變過程,因此以燃料高位發(fā)熱量來計(jì)算會(huì)使純碳實(shí)際燃燒過程的熵產(chǎn)增加,對(duì)能源利用過程而言,這種影響是符合客觀規(guī)律的。甲烷在一定燃燒溫度范圍內(nèi)以高位發(fā)熱量來計(jì)算反應(yīng)熵是正值,結(jié)果符合真實(shí)性。但在高溫燃燒時(shí)的反應(yīng)熵出現(xiàn)負(fù)值,因此當(dāng)燃燒溫度較高時(shí)應(yīng)重新選取甲烷的發(fā)熱量來計(jì)算過程參數(shù)。辛烷燃燒的反應(yīng)熵均為正值且隨燃燒溫度的升高不斷增大,盡管結(jié)果也符合實(shí)際情況,但為使燃料的燃燒效率達(dá)到最高,應(yīng)合理控制燃燒溫度,使過程不可逆損失降到最低。本文的分析結(jié)果可以作為燃料高效燃燒優(yōu)化設(shè)計(jì)的理論依據(jù),為能源高效清潔使用的進(jìn)一步加強(qiáng)提供指導(dǎo)性方向。同樣應(yīng)用單耗分析理論對(duì)燃?xì)庖徽羝?lián)合循環(huán)某9F等級(jí)余熱鍋爐進(jìn)行了熵產(chǎn)分析,以熱力學(xué)等價(jià)為前提建立了不同循環(huán)系統(tǒng)內(nèi)部各種不可逆損失所引起的熵產(chǎn)分析模型,并通過實(shí)例對(duì)此模型進(jìn)行了驗(yàn)證。結(jié)果顯示高壓水循環(huán)系統(tǒng)的熵產(chǎn)占余熱鍋爐總熵產(chǎn)的份額較大,發(fā)掘節(jié)能潛力應(yīng)從高壓水循環(huán)系統(tǒng)入手。該模型的提出旨在于應(yīng)用第二定律分析方法對(duì)無燃料燃燒的換熱過程進(jìn)行效率評(píng)估,為能源利用的第二定律審計(jì)工作提供一套集科學(xué)性、完整性和嚴(yán)謹(jǐn)性于一體的審計(jì)體系。
[Abstract]:In all forms of fuel utilization, the combustion process is a necessary process for converting the chemical energy of the fuel into heat energy. Because of the complexity of fuel composition and the mixing of several substances, combustion products are difficult to be measured by the first law of thermodynamics in the analysis of combustion efficiency. The process of fuel utilization should be analyzed concretely, not only in the beginning and end of the process, but also in the process itself. In this paper, three different fuels, carbon, methane and octane, are taken as examples, and based on the theory of unit consumption analysis, the fuels in different states represented by these three fuels are discussed. The reaction enthalpy, reaction free enthalpy, reaction entropy and the proportion of irreversible loss of heat in the combustion process of these three fuels at different temperatures are calculated by simplified analysis. The results show that the reaction entropy of pure carbon combustion is positive and there is no water vapor phase transition process. This effect is in line with the objective law. In the range of combustion temperature, the reaction entropy of methane is calculated with high calorific value, and the results agree with the reality. However, the reaction entropy of high temperature combustion is negative, so when the combustion temperature is high, the heat of methane should be re-selected to calculate the process parameters. The reaction entropy of octane combustion is all positive and increases with the increase of combustion temperature. Although the results accord with the actual situation, in order to achieve the highest combustion efficiency of fuel, the combustion temperature should be controlled reasonably and the irreversible loss of the process should be reduced to the minimum. The results of this paper can be used as the theoretical basis for the optimization design of fuel efficient combustion and provide guidance for the further strengthening of energy efficiency and clean use. The entropy production of a 9F grade waste heat boiler in a gas-steam combined cycle is also analyzed by using the unit consumption analysis theory. Based on the premise of thermodynamic equivalence, an analysis model of entropy production caused by various irreversible losses in different circulation systems is established. The model is verified by an example. The results show that the entropy production of the high pressure water circulation system accounts for a large proportion of the total entropy production of the waste heat boiler, so we should start with the high pressure water circulation system to explore the energy saving potential. The purpose of this model is to evaluate the efficiency of the heat transfer process without fuel combustion by using the second law analysis method, and to provide a scientific, complete and rigorous audit system for the audit of the second law of energy utilization.
【學(xué)位授予單位】：華北電力大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TK16

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